1. Field of the Invention
The invention relates to a display device for commercial television, computer displays, and displays used for conferences, and more particularly to a flat CRT display device.
2. Description of the Prior Art
FIG. 15 shows a flat display such as that disclosed in the proceedings of the Fourth International Vacuum Micro-Electronics Conference. The display device has a plurality of electron emitting elements which emit electrons under the influence of an electric field. In FIG. 15, the numeral 1 denotes a first base substrate which is made of glass, and the numeral 2 a front glass panel which is made of glass. Numeral 3 indicates a side wall, and 5 a fluorescent film mounted on the front glass panel 2. Cathode electrode 6 emits electrons. The numeral 7 denotes a transparent anode electrode formed on the fluorescent film 5. The interior space surrounded by the first base substrate 1, the front panel 2, and side wall 3 forms a vacuum region, where the degree of vacuum is maintained at about 10.sup.-3 .about.10.sup.-5 Torr.
Also in FIG. 15, printed wiring 8 leads the cathode electrode 6 to an outside power source (not shown). Printed wiring leads (not shown) the transparent anode electrode 7 to the positive terminal of the outside power source.
The electron emitting elements are formed on the first base substrate 1. The numeral 31 denotes an electron emitting emitter from which electrons are emitted. The electrons are emitted from the emitter 31 to the anode electrode 7 under the influence of the electric field established between the anode electrode 7 and the cathode electrode 6. The numeral 32 denotes a gate electrode which controls the flow of electrons emitted from the emitter electrode 31. The gate electrode 32 and the cathode electrode 6 are arrayed in a matrix in the longitudinal and transverse directions. The brightness of a picture element in the flat CRT display is determined by applying voltage between the gate electrode 32 and the cathode electrode 6 corresponding to the picture element. The emitted electrons are accelerated vertically against the cathode electrode 6 by the anode electrode 7 and strike the fluorescent film 5 to generate light.
Numeral 33 designates an insulation material which separates the gate electrode 32 from the cathode electrode 6.
As mentioned, a detailed description of such a display device is described in the proceedings of the Fourth International Vacuum Micro-Electronics Conference.
It is difficult to manufacture a display device of the above configuration which has a large surface. This is because it is necessary to manufacture a large-sized glass substrate having a plurality of electron emitting elements on it which is the same size as the screen. The electron emitting elements are formed on the glass substrate by precision manufacturing processes such as photolithography, deposition, and etching processes. Since the element size is very small (for example, on the order of microns), failures may occur when fine extraneous materials stick on the electron emitting elements in its fabrication process.
When the size of the display device becomes larger, the probability of failure of a part of the display device increases exponentially. If a failure occurs on any part of the electron emitting elements, the entire display device having the electron emitting elements cannot be used because the effects of the failure appear clearly on the screen. Therefore, it is very difficult to manufacture a screen having a large-sized substrate, for example, on the order of 20.about.50 inches.